SIMULASI MCNP5 DALAM EKSPERIMEN KRITIKALITAS LARUTAN PLUTONIUM–URANIUM NITRAT DENGAN REFLEKTOR AIR DAN POLYETHYLENE

SIMULASI MCNP5 DALAM EKSPERIMEN KRITIKALITAS LARUTAN PLUTONIUM DAN URANIUM NITRAT DENGAN REFLEKTOR AIR DAN POLYETHYLENE. Banyak perangkat kritik dibangun untuk memenuhi kebutuhan studi fenomena kecelakaan kritikalitas pada larutan fisil di fasilitas daur bahan bakar nuklir. Salah satu diantaranya adalah perangkat kritik SCAMP. Di perangkat ini dikerjakan eksperimen kritikalitas menggunakan bejana silindris stainless steel berisi larutan plutonium- uranium nitrat (Pu+U nitrat). Sebanyak 7 eksperimen didemonstrasikan dengan reflektor air di semua sisi permukaan bejana larutan kecuali di bagian atas bejana. Makalah ini membahas simulasi transport Monte Carlo MCNP5 dalam eksperimen kritikalitas larutan Pu+U nitrat dengan reflektor air dan polyethylene. Simulasi MCNP5 dengan pustaka ENDF/B-VI memberikan hasil yang paling dekat dengan data eksperimen terutama pada kasus A untuk varian geometri 4. Dibandingkan pustaka ENDF/B-V, perhitungan kritikalitas dengan pustaka ENDF/B-VI memberikan hasil lebih dekat dengan perhitungan MONK dimana bias perhitungannya < 0,44%, khususnya pada kasus A namun pada kasus B dan C simulasi MCNP5 dengan pustaka ENDF/B-V memberikan hasil dengan kecenderungan lebih baik dibandingkan pustaka ENDF/B-VI dengan bias perhitungan < 2,67% dan < 1,13%. Secara keseluruhan dapat disimpulkan bahwa MCNP5 telah menunjukkan reliabilitasnya dalam simulasi kritikalitas larutan Pu+U nitrat. Kata kunci: kritikalitas, larutan Pu+U nitrat, ENDF/B-V, ENDF/B-VI, MCNP5 MCNP5 SIMULATION IN CRITICALITY EXPERIMENT OF PLUTONIUM–URANIUM NITRATE SOLUTION WITH WATER AND POLYETHYLENE REFLECTORS. There are many critical assemblies have been built to meet the need of criticality accident phenomenon study on fissile solution at nuclear fuel cycle facilities. One of them is critical assembly SCAMP. In this assembly the criticality experiments were carried out by using stainless steel cylindrical vessel containing plutonium-uranium nitrate solution (Pu+U nitrate). 7 Experiments have been demonstrated with water reflector at all surface areas of solution vessel except on the top vessel. This paper discusses simulation of Monte Carlo transport MCNP5 in criticality experiment of P+U nitrates solution with water and polyethylene reflectors. Simulation MCNP5 with ENDF/B-VI library gives closest results with experimental data, especially in the case A for geometry variant 4. Compared to ENDF/B-V library, criticality calculations with ENDF/B-VI library give closer results with MONK calculations where its calculation bias is < 0.44%, especially in the case A but in the case B and C, MCNP5 simulation with ENDF/B-V library give results with a better tendency than ENDF/B-VI library with calculation biases of < 2.67% and < 1.13%. All in all, it can be concluded that MCNP5 has indicated its reliability in criticality simulation of Pu+U nitrate solution. Keywords: criticality, Pu+U nitrate solution, ENDF/B-V, ENDF/B-VI, MCNP